| 1. |
- Hoglund, L, et al.
(författare)
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Selective optical doping to predict the performance and reveal the origin of photocurrent peaks in quantum dots-in-a-well infrared photodetectors
- 2009
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Ingår i: INFRARED PHYSICS and TECHNOLOGY. - Exeter : Elsevier BV. - 1350-4495 .- 1879-0275. ; 52:6, s. 272-275
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Tidskriftsartikel (refereegranskat)abstract
- Resonant optical pumping across the band gap was used as artificial doping in InAs/In0.15Ga0.85As/GaAs quantum dots-in-a-well infrared photodetectors. Through efficient filling of the quantum dot energy levels by simultaneous optical pumping into the ground states and the excited states of the quantum dots, the response was increased by a factor of 10. Low temperature photocurrent peaks observed at 120 and 148 meV were identified as intersubband transitions emanating from the quantum dot ground state and the quantum dot excited state, respectively by a selective increase of the electron population in the different quantum dot energy levels.
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| 2. |
- Hsiao, C.L., et al.
(författare)
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High-phase-purity zinc-blende InN on r -plane sapphire substrate with controlled nitridation pretreatment
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:11
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Tidskriftsartikel (refereegranskat)abstract
- High-phase-purity zinc-blende (zb) InN thin film has been grown by plasma-assisted molecular-beam epitaxy on r -plane sapphire substrate pretreated with nitridation. X-ray diffraction analysis shows that the phase of the InN films changes from wurtzite (w) InN to a mixture of w-InN and zb-InN, to zb-InN with increasing nitridation time. High-resolution transmission electron microscopy reveals an ultrathin crystallized interlayer produced by substrate nitridation, which plays an important role in controlling the InN phase. Photoluminescence emission of zb-InN measured at 20 K shows a peak at a very low energy, 0.636 eV, and an absorption edge at ∼0.62 eV is observed at 2 K, which is the lowest bandgap reported to date among the III-nitride semiconductors. © 2008 American Institute of Physics.
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| 3. |
- Höglund, Linda, 1974-, et al.
(författare)
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Bias and temperature dependence of the escape processes in quantum dots-in-a-well infrared photodetectors
- 2008
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Ingår i: Applied Physics Letters. - New York : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 93:10, s. 103501-
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Tidskriftsartikel (refereegranskat)abstract
- The performance of quantum dots-in-a-well infrared photodetectors (DWELL IPs) has been studied by means of interband and intersubband photocurrent measurements as well as dark current measurements. Using interband photocurrent measurements, substantial escape of electrons from lower lying states in the DWELL structure at large biases was revealed. Furthermore, a significant variation in the escape probability from energy states in the DWELL structure with applied bias was observed. These facts can explain the strong temperature and bias dependence of both photocurrent and dark currents in DWELL IPs.
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| 4. |
- Höglund, Linda, 1974-, et al.
(författare)
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Bias mediated tuning of the detection wavelength in asymmetrical quantum dots-in-a-well infrared photodetectors
- 2008
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Ingår i: Applied Physics Letters. - New York : AIP Publishing. - 0003-6951 .- 1077-3118. ; 93:20
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Tidskriftsartikel (refereegranskat)abstract
- Bias-mediated tuning of the detection wavelength within the infrared wavelength region is demonstrated for quantum dots-in-a-well and dots-on-a-well infrared photodetectors. By positioning the InAs quantum dot layer asymmetrically in an 8 nm wide In0.15Ga0.85As/GaAs quantum well, a shift in the peak detection wavelength from 8.4 to 10.3 mu m was observed when reversing the polarity of the applied bias. For a dots-on-a-well structure, the peak detection wavelength was tuned from 5.4 to 8 mu m with small changes in the applied bias. These tuning properties could be essential for applications such as modulators and dual-color infrared detection.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Höglund, Linda, 1974-, et al.
(författare)
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Optical pumping as artificial doping in quantum dots-in-a-well infrared photodetectors
- 2009
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Ingår i: Applied Physics Letters. - New York : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:5, s. 053503-
-
Tidskriftsartikel (refereegranskat)abstract
- Resonant optical pumping across the band gap was used as artificial doping in InAs/In0.15Ga0.85As/GaAs quantum dots-in-a-well infrared photodetectors. By selectively increasing the electron population in the different quantum dot energy levels, the low temperature photocurrent peaks observed at 120 and 148 meV, could be identified as intersubband transitions emanating from the quantum dot ground state and the quantum dot excited state, respectively. With efficient filling of the quantum dot energy levels through simultaneous optical pumping into the ground states and the excited states of the quantum dots, the response was increased by a factor of 10.
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| 9. |
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| 10. |
- Höglund, Linda, 1974-, et al.
(författare)
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Optimising uniformity of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy
- 2006
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 252:15, s. 5525-5529
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Tidskriftsartikel (refereegranskat)abstract
- A route towards optimisation of uniformity and density of InAs/(InGaAs)/GaAs quantum dots grown by metal organic vapor phase epitaxy (MOVPE) through successive variations of the growth parameters is reported. It is demonstrated that a key parameter in obtaining a high density of quantum dots is the V/III ratio, a fact which was shown to be valid when either AsH3 (arsine) or tertiary-butyl-arsine (TBA) were used as group V precursors. Once the optimum V/III ratio was found, the size distribution was further improved by adjusting the nominal thickness of deposited InAs material, resulting in an optimum thickness of 1.8 monolayers of InAs in our case. The number of coalesced dots was minimised by adjusting the growth interruption time to approximately 30 s. Further, the uniformity was improved by increasing the growth temperature from 485 °C to 520 °C. By combining these optimised parameters, i.e. a growth temperature of 520 °C, 1.8 monolayers InAs thickness, 30 s growth stop time and TBA as group V precursor, a full-width-half-maximum (FWHM) of the low temperature luminescence band of 40 meV was achieved, indicating a narrow dot size distribution.
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